The stick contains a dossier of material about the businessman which, he alleges, evidences a conspiracy to damage him.

The USB stick was in the offices of Digipol, a firm in Rotterdam, for some 10 days after the court ordered on October 16 last it be handed over "forthwith" to solicitors for Mr O'Brien to be held without interference pending further court orders, Maurice Collins SC, for Red Flag, said yesterday.

Martin Hayden SC, for Mr O'Brien, said there had been no access to, or interference with, the encrypted chamber of the USB stick containing the dossier. Digipol had the stick for analysis purposes and what was being suggested by Red Flag was "outrageous".

Mr O'Brien initiated his case in October after the USB stick was sent anonymously in an envelope to his Dublin office. He alleges conspiracy and defamation against Red Flag and some of its executives and staff.

A hearing date has yet to be fixed and the case was before Mr Justice Colm MacEochaidh for case management purposes.

Mr Collins said his side is very concerned about issues concerning custody of the USB stick.

Red Flag was unaware the stick was with Digipol in Rotterdam until October 26 and was informed on October 29 it was in the custody of Mr O'Brien's solicitors without being told it had only come into their possession.

His side was also concerned with what was happening when the stick was surrendered to another digital forensic firm, Espion, in the solicitors' offices.

His side was concerned there appeared to have been disregard of the court's October 16 order, he said.

Mr Hayden said he took issue with the "outrageous" way these matters were being raised and the "emotive language" used.

Mr Justice MacEochaidh noted his October order directed the stick be handed over "forthwith" and gave Mr O'Brien's side two weeks to provide an affidavit addressing the issues raised.